NEW YORK - ConocoPhillips, the nation's third-largest oil company, says it will split itself into two separate publicly traded companies and its CEO and Chairman Jim Mulva plans to retire once the transaction is complete.

Its shares jumped almost 5 percent in premarket trading.

Conoco said Thursday its board has approved separating the company's refining and marketing and exploration and production businesses by spinning off the refining and marketing segment to shareholders in a tax-free transaction.

The split, which is expected to be completed during the first half of next year, will leave Conoco as an exploration and production company.

It says Mulva will lead the separation efforts, but plans to retire once the split is complete.

Conoco says its separation plans do not require a shareholder vote.

The Houston-based company has about 29,600 employees.